Shaw McIntyre shares a close bond with the Rack family from Virginia in the US - one of them even shares his DNA.

Eleven years ago Shaw, from West Lothian, and his wife joined the Anthony Nolan bone marrow register following the death of her mother.

Within months the register had found a leukaemia patient to receive Shaw's bone marrow, but at that stage he was not told who it was.

"I didn't know anything about where it was going or who needed it. It didn't matter," the 45-year-old said.

Firm friends

But he admitted he remained curious about who had benefited and received three-monthly updates about how the transplant had gone.

A year after the donation, he was told the recipient had been two-year-old Rachel Rack.

"When I found out that Rachel was only two at the time, that meant a sharp intake of breath as I had a daughter the very same age.

We feel a gratitude to Shaw that you really can't put into words. We don't know how to repay him, but we are like family now

Rachel Rack's mother Mary

"We started corresponding in late 1997 and I decided to go over and visit for Thanksgiving. The Rack family were very welcoming and they showed me about Virginia and then I took over my whole family.

"I have been over every year since, but this year they came to visit Scotland for the first time."

Rachel's mother, Mary, said her daughter had been very ill with leukaemia when she received the cells, but that Shaw had been a perfect match.

"We were very hopeful. We knew though that there were many stepping stones we would have to cross," Mary said.

"She had lots of friends she had made over the years, while having chemo, who did not make it, so we were very fearful.

The procedure is relatively painless for donors, experts say

"We knew we had to take every day at a time and she was so little and she had so much to go through."

Rachel was in hospital for about a month. First she went for daily checks. Now these are annual.

Mary urged others to join the bone marrow register.

"We feel a gratitude to Shaw that you really can't put into words. We don't know how to repay him, but we are like family now. We have made a wonderful friend.

"It is just so very important to sign up you just don't know whose life you could save."

Register appeal

There are currently 7,000 people globally who need a bone marrow transplant, but the chances of finding a match are slim because the genetic make-up is so varied.

The Anthony Nolan Trust is urging more people aged between 18 and 40 to register as donors.

Experts say they particularly need male donors aged between 18 and 25 as they can generally provide a greater volume of blood stem cells, which aid recovery.

We need many people on the register to ensure we get as many matches and tissue types as possible

Dr Paul Travis, Scottish Centre for Regenerative Medicine

Pauline Makoni, of the trust, said men of this age currently make up just 10% of the register.

"We always need more donors for the register.

"When they turn 60 we remove them from the register or they might be excluded for medical reasons or personal reasons, so we never reach a point where we can say we have enough donors for the time being," she said.

"Probably the main inconvenience to the donor is the time factor. It is not a one-day procedure."

Dr Paul Travis, of the Scottish Centre for Regenerative Medicine said: "It is a relatively simple procedure. It is not a really big operation.

"But we need many people on the register to ensure we get as many matches and tissue types as possible.

"If the tissue types are not matched the body will think of them as being something which needs to be eliminated.

"You really do need the greatest possible donors out there to get a match."